1. Field of the Invention
This invention relates to a data communication system, and, more particularly, it is concerned with an image forming apparatus which constitutes a part of the data communication system for carrying out transmission of information such as image information, etc., through signal transmission paths such as optical fiber cables, and so forth.
2. Description of the Prior Art
There have so far been proposed or put into practice various systems for performing transmission and receipt of informations between distant locations. The system is, in general, of such a construction that information processing devices having signal transmission and receiving functions are put into connection by means of signal transmission channels, through which the informations are sent. As one example of such image transmission system, it may be contemplated that a reading device to read an image original and to form image signals is joined with a printing device to record the image based on the image signals by the signal transmission paths such as, for example, optical fiber cables so that the image information which has been read at the first location may be recorded at the second location. In the system of performing transmission and receipt of information between or among a plurality of reading and printing devices which are connected by signal transmission paths using the optical communication system, it is often necessary that a repeater be located at every several kilometers to ten and several kilometers, when the distance between the neighboring devices is fairly long, to compensate attenuation in the light signals being transmitted through the signal transmission paths connecting the devices. The electric power supply for driving the repeaters is generally taken from the commercial power source, or from a house generator provided in each of the repeaters. However, when any one of the repeaters stops its operation due to interruption in the current supply or trouble with the generator, the communication system as a whole would be interrupted by the defunct repeater to result in disabled communication.
On the other hand, a communication system, wherein signal processors to carry out operations such as image formation, etc., based on information sent through the signal transmission path are connected in a loop, is generally of such a construction that it may determine whether the signals from the transmitter have been duly received at the receiving station or not, by return of the signals to the transmitting station from which they were originated, around through the loop. In this communication system, it is indispensable that the power supply be always given to the entire signal processing devices connected in loop, even when some of them alone are used for the communication operations, and yet the whole devices be in regular operative conditions. Apparently, such system wastes the electric power because of the power supply to those devices not in need of use.